Propulsion unit for multihull such as a catamaran

ABSTRACT

The invention concerns a propulsion unit for a multihull such as a catamaran, comprising at least one turbine, seawater suction means and seawater backflow means. The invention is characterized in that said device comprises a seawater turbine directly driven by a motor inside each of the hulls ( 1 ), the seawater suction means being positioned at the front, outside each hull ( 1 ) in an overpressure zone generated by the bow wave and the seawater backflow means being positioned inside each hull ( 11 ), on the rear of the boat pitch pivot pin, said backflow means having an outlet ( 5 ) capable of being pivoted and emerging inside the channel defined between two hulls ( 1 ).

The present invention concerns a propulsion unit for multihull boatssuch as catamarans.

The boat propulsion units are used, on the one hand, for port andpositioning maneuvers and, on the other, for transit. These two types ofuse require, however, different properties. In fact, port andpositioning maneuvers require great flexibility and little power, whiletransit demands high power making it possible to attain maximum speed,while necessitating little or no maneuvers.

It is therefore necessary to propose boat propulsion units making itpossible to access those two types of use satisfactorily.

Standard propulsion units generally consist of three main parts, whichare the power generating means (engine or turbine), the means using thepower (propeller or jet) and the means ensuring transmission among them.

Thus, propulsion units can comprise a engine, a speed reducer, a clutch,a reverser, a thrust bearing, a shaft line and a propeller. Otherpropulsion units consist of an engine, a multiplier, the shortestpossible shaft line and a jet turbine equipped with an inversion chamberand a thrust bearing. These propulsion units can also contain a gas orsteam turbine, a speed reducer, a thrust bearing and a propeller or jetturbine.

Now, it has been observed that to obtain good efficiency and not foulup, the engines must run at approximately 2,000 rpm, while the turbinesmust run at 8,000 rpm at least, in order to have power.

Likewise, in order to have power, the jets must run at approximately3,000 rpm, while the propellers must average 100 rpm to obtain goodefficiency.

In the case of engine and turbine units, the result is generally toomuch power during maneuvers, which disrupts their good performance.Furthermore, in the case of an engine and propeller unit, the clutch andthe propeller must be stopped between each maneuver, which results inboth a waste of time and squandering power in order to restart.

In the case of a jet propulsion unit, the minimum power required forgood operation can damage the docks on port maneuvers. Furthermore, thesuction of the jets generally placed under the hull can result atshallow depth in the suction of sand and mud capable of damaging theturbine blades.

Hydraulic propulsion units of vessels, situated in the hull of amonohull, have been described. Thus, in U.S. Pat. No. 512,591, amonohull is proposed with suction means proposed in front on each sideof the hull toward the turbines and backflow means on both sides of thesingle hull and in the rear. In US document 2002/037,675 a propulsionsystem is described mounted in the hull of a boat, such as a yacht or apleasure trawler, comprising symmetrical exhaust pipes, water inlets onboth sides of the hull, near the bow and connected to the pipes, amixing chamber, nozzles at the pipe opening and at least one pump gearin each pipe, driven by a motor.

GB 1,194,510 proposes seawater suction for a monohull at the front ofthe boat toward a pump driven by a motor and connected to that pipe andtwo steering units situated on the center line of the boat, one towardthe front and the other toward the rear, each steering unit consistingof a water backflow nozzle that can change direction.

In document DE 3,125,887, a catamaran is provided with a channelcrossing each floating body from an inlet in front, at the front end ofthe float (dead center), to the rear end, the channel being connected toa pressure generator placed on the deck between each float, so thatwater is sucked in front with a view to creating “impulse water” and isexpelled in the rear by an outlet nozzle or else is expelled as “brakewater” in front through the front channel opening. Such a unit isconceivable only in a float catamaran rather than hull catamaran system,the problems not being the same.

Furthermore, in the case of catamaran-type boats, the propulsion unitshave to be adapted to the specific problems associated with the shape ofthe boat. In particular, on picking up speed, a standard catamaran tendsto sink back, thus increasing the wet surface of the hulls and the drag.

The object of the present invention is, therefore, to propose apropulsion unit for multihulls, such as a catamaran, overcoming thoseproblems by making it possible to obtain good performance during portmaneuver phases as well as during transit phases.

The object of the present invention is thus a propulsion unit formultihull boats, such as a catamaran, comprising, notably, at least oneturbine, seawater suction means and seawater backflow means,characterized in that it contains a seawater turbine driven directly byan engine in each of the hulls, the seawater suction means beingpositioned in front preferably outside each hull in an overpressure zonegenerated by the bow wave and the seawater backflow means beingpositioned in each hull on the rear of the boat pitch pivot pin, saidbackflow means having an outlet capable of pivoting and emergingpreferably inside the channel defined between two hulls.

Advantageously, the propulsion unit according to the invention is thusparticularly well-integrated to the specific shape of a multihull and,in particular, a catamaran and thus exploits all the advantages.

The suction means are preferably positioned on the front outside eachhull in an overpressure zone linked to the bow wave, affording theturbines natural supercharging.

When the outlets of the backflow means are turned vertically downward orupward, no propulsive force is produced on starting the engines, whichmakes it possible not to provide a clutch between the engine and theturbine.

Thus, the propulsion unit according to the invention is considerablysimplified, inasmuch as the outlet of the pivoting backflow means allowthe absence of a clutch between engine and turbine. Furthermore, theabsence of moving parts in the water eliminates the problems of lockingwhich can occur with propellers, as well as the risks of deteriorationor jamming of the latter. Furthermore, there is no longer any danger fordivers, as might be the case of a boat equipped with a propeller.

According to a preferred embodiment of the invention, the seawaterbackflow means consist of at least one pivoting elbowed nozzle.

That nozzle consists of a first tube, in which a second tube is pivoted,of diameter slightly less than that of the first tube. The difference indiameter between the tubes can be compensated by sleeving of the innertube pivoting by means of a “slippery” material compatible with theseawater, such as a PVC-type plastic, a polyamide like that known by thetrade name “Ertalon.” Housings are cut into the sleeving in order toreceive the O-ring seals ensuring tightness between the tubes.

The tubes used can advantageously be stainless steel tubes of standarddiameters or else tubes of a similar appropriate material.

At one end of the inner tube, there is a reduction cone (ratio close to2/1, for example), making possible water jet pressure, the elbow oroutlet nozzle being welded to the cone on the small diameter side.

Thus, each outlet nozzle or elbow can be rotated between two outletpositions of the water jet downward or upward, in which no propulsiveforce is produced, the outlet positions of the water jet of the frontand rear motions being at 90° from either vertical position.

The means making it possible to rotate the outlet nozzles consist ofcables, chains, pinion rods or the like, automatically or manuallycontrolled without stopping the engine. These drive means are welded tothe base of the outlet elbow near the reduction cone, the cables, chainsor rods passing inside vertical tubes welded to the outer tube of thenozzle and rising well above the water level, which makes it possible toavoid the placement of expensive and unreliable stuffing boxes. Thesemeans of rotating the nozzles can be actuated without having to stop theengine.

Consequently, to control the propulsion of the boat, it is sufficient toturn the outlet nozzles forward to secure backward propulsion andbackward to secure forward propulsion.

When the outlet nozzles are turned vertically downward, they canadvantageously help refloat the boat, especially considering that thequantity of water ejected produces an underwashing effect under thehulls.

An intermediate position of the outlet nozzles and, consequently, of thetubes pivoting at 45° from either of the vertical positions makes itpossible to block, at least in large part, the delivery of the outletnozzle and/or to place the openings existing in each of the tubes,pivoting or stationary, opposite each other. When those openings areopposite, the backflow jets are directed to pipes ending in a nozzleconnected to the rudder post for one of them, and in a pivoting nozzlesituated under a third bow for the other (that nozzle can deliver onlyunder the effect of pressure).

The horizontal forces thus obtained advantageously make it possible tomove the boat in all directions, assuring a manual dynamic positioning.

These secondary nozzles also make swinging in place possible.

The propulsion unit according to the invention likewise makes itpossible to control and diminish deck movements such as roll and pitch.

Thus, the outlet nozzles being at the rear of the pitch pivot pin of theboat, the oscillation of those nozzles around the “forward motion”position can create a torque countering that generated by the pitch.

Likewise, by using the propulsion unit according to the invention indynamic positions, as previously described, and providing sphericalvalves, manually controlled, for example, mounted on the pipes in frontand in back, trimming tanks, one situated in front and the other in therear in the space between hulls, can be filled rapidly. Thus, if theboat dips its head, the rear trimming tank is filled, while rapidlyemptying the front trimming tank by gravity, and the opposite maneuveris performed if the front is lightened.

The tanks can also be filled to make the boat heavier when grounded, sothat it will not be subjected to swells.

To control the roll, the tanks formed by walls of the hull, lined insidethe boat by a bulkhead going from the upper deck to the water level, arefilled, as described above. These tanks further constitute a double hulladvantageous in case of collision, which reduces the infrared radiationand can serve as protection in case of small arms firing.

The propulsion unit according to the invention can further containadditional means of propulsion or “boosters” set up at the back of theengines of said unit.

Such additional propulsion means are chosen in accordance with the sizeof the boat and its use. Thus, a self-contained motor pump unit of thetype used by firemen can be employed. Their compactness, that is, theyare simply placed in the hull and connected to the suction means and thebackflow means, makes it possible to easily remove them for maintenance.Provision can also be made for the use of turbines of the same type ason helicopters.

The power supply of that motor pump unit is situated in front as low aspossible in the channel between the hulls and as close as possible tothe corresponding backflow under each hull in the back of the groundingplane. These means of propulsion are started without clutch and withoutrear motion, since they are employed only when high speed is sought orelse when a propulsion unit according to the invention is used tocontrol the roll.

The propulsion unit according to the invention is particularlywell-suited for a catamaran, whose channel between hulls provides aVenturi effect, as described in patent EP 0,108,004, which proposes acatamaran-type boat with two hulls symmetrically arranged in relation toa mean vertical plane and joined by a connecting bridge above the waterline, each hull being dissymmetrical to a vertical plane passed throughthe bow and parallel to the mean vertical plane, with a half main framelarger and more advanced on the inner side than on the outer side, whiletoward the rear, from the main frame, the inner wall of each hull is inthe form of an appreciably helicoidal surface with horizontalgeneratrices, the upper generatrix being roughly parallel to themidplane of the boat and a lower generatrix coming under the hull. Thisparticular geometry of each hull leads to defining a Venturi shape ofthe channel between the two hulls adding and controlling the interiorbow waves, which tends to produce a lifting of the front of the boat,while the exterior bow waves are reduced. Such a boat, therefore, makesit possible to recover in positive action a part of the energy containedin the wave train formed in order to improve its navigation performance,particularly by lightening the boat in the rear and also in front and bylimiting dipping of the rear.

Thus, the pivoting elbowed nozzles positioned in the rear of the pitchpivot pin of the boat preferably spit out seawater also in the rear ofthe Venturi neck in a zone where the wave train causes a slightdepression to appear, which produces less back pressure on outlet.Furthermore, the jets are supported on the specific stationary wave ofthe boat and increases its volume. This advantageously results in thefollowing wave forming part of the wake to be captive in the channelbetween hulls and contributes to propulsion.

Somehow integrated with the specific shapes of this hull, the propulsionunit thus has excellent efficiency and affords remarkablemaneuverability.

The propulsion unit according to the invention can advantageously equipmultihulls, such as catamarans of all sizes, that is, from a smallpleasure craft to a large carrier.

The invention will now be described more in detail, with reference tothe attached drawing in which:

FIG. 1 represents a view in front perspective of a catamaran equippedwith a unit according to the invention;

FIG. 2 represents a cross section of the pivoting elbowed nozzles of apropulsion unit according to the invention;

FIG. 3 represents a lateral perspective of a rudder of a boat equippedwith a unit according to the invention; and

FIG. 4 represents a sectional view of the lower part of a boat hullequipped with a nozzle according to FIG. 2.

The propulsion unit according to the invention is intended to beinstalled on multihulls, such as the catamaran C illustrated in FIG. 1with two hulls 1 and a third bow 2.

This unit contains a seawater turbine directly driven by an engine ineach of the hulls 1, seawater suction means positioned in front outsideeach hull 1 in an overpressure zone generated by the bow wave andseawater backflow means positioned in the rear inside each hull 1, onthe back of the pitch pivot pin of the boat, said backflow means havingan outlet capable of pivoting. In the unit according to the invention,it is possible to use turbines, such as those employed in boatyards andwhich can accept pebbles, sand, gravel, etc. without damage.

The seawater backflow means comprise a pivoting elbowed nozzle 3consisting of a first tube 3 a, in which a second tube 3 b is pivoted,of diameter slightly less than that of the first tube 3 a. Thedifference in diameter between the two tubes 3 a, 3 b is compensated bysleeving M of the inner tube pivoting by means of a slippery materialcompatible with the seawater, such as a polyamide, or the like.Tightness between the tubes 3 a and 3 b is obtained by O-ring seals (notrepresented) placed in housings cut into the sleeving.

At one end of the inner tube 3 b, there is a reduction cone 4 makingwater jet pressure possible, the elbow or outlet nozzle 5 being weldedto the cone 3 b on the small diameter side.

The outer tube 3 a is fastened inside the hull and perpendicular to theaxis of the craft, while the inner tube 3 b is engaged outside the hull(not represented in FIG. 2) in the tube 3 a across the opening machinedin the hull. There is then no risk of leakage.

Furthermore, a locking plate 8 is engaged on the outlet nozzle 5 andfastened outside the hull. That locking plate 8 has, in addition, acircular sector which makes it possible to block the opening of theoutlet nozzle 5 at least partially when it is brought into a 45°position forward and upward. That circular sector also makes it possibleto at least partially protect the outlet nozzle 5.

The locking plate 8 preferably also contains a rolling system whichcollects the thrust of the reduction cone on backflow or else a flatsliding joint.

As can be seen in FIG. 4, the pivoting elbowed nozzle is installed inthe hull 1 at the bilge level (that is, the rounded lower part joiningthe grounding plane and the wall of the hull 1).

Thus, the outlet nozzle or elbow 5 can be rotated between two outletpositions of the water jet downward or upward, in which no propulsiveforce is produced, the outlet positions of the water jet of the frontand rear motions being at 90° from either vertical position.

An intermediate position of the outlet nozzles 5 and, consequently, ofthe tubes 3 a, 3 b pivoting at 45° from either of the vertical positionsmakes it possible to block, at least in large part, the opening of theoutlet nozzle 5, thanks to the circular sector of the locking plate 6,and/or to place the openings existing in each of the tubes 3 a, 3 bopposite each other.

When those openings are opposite, the backflow jets are directed topipes ending in a nozzle 6 connected to the rudder post 7 for one ofthem, as shown in FIG. 3, and in a pivoting nozzle situated under athird bow 2 of the catamaran C for the other.

The rudder post 7 has a rear part 7 a and a compensating front part 7 benabling the rudder 7 to collect the thrust forces associated withpropulsion by the nozzle 6. The rudders rotates over the whole horizon.

The upper corner of the front part 7 b contains a support device such asa roller bearing on the hull, preventing bending of the hollow postunder the effect of thrust.

1. Propulsion unit for multihulls such as a catamaran, having at leastone turbine, seawater suction means and seawater backflow means,characterized in that the propulsion unit comprises a seawater turbinedirectly driven by an engine in each of the hulls, seawater suctionmeans positioned in front preferably outside each hull in anoverpressure zone generated by the bow wave and seawater backflow meanspositioned in the rear inside each hull, on the back of a pitch pivotpin of the multihull, said backflow means having an outlet capable ofpivoting and emerging inside a channel defined between two hulls. 2.Unit according to claim 1, characterized in that the suction means arepositioned in front outside each hull in an overpressure zone linked tothe bow wave affording the turbines natural supercharging.
 3. Unitaccording to claim 1, characterized in that the seawater backflow meanscomprise at least one pivoting elbowed nozzle consisting of a firsttube, in which a second tube is pivoted, of diameter slightly less thanthat of the first tube, a reduction cone enabling the pressure of thewater jet at one end of the inner tube and an elbow or outlet nozzlewelded to the cone on the small diameter side.
 4. Unit according toclaim 3, characterized in that the difference in diameter between thetubes is compensated by sleeving of the inner tube pivoting by means ofa material compatible with the seawater, housings being cut into thesleeving to receive the O-ring seals ensuring tightness between thetubes.
 5. Unit according to claim 3, characterized in that the outertube can be fastened inside the hull opposite an opening machined insaid hull, while the inner tube can be engaged outside the hull in thetube across the opening machined in the hull, and a locking plate can beengaged on the outlet nozzle and fastened on the outside of the hull. 6.Unit according to claim 3, characterized in that an outlet nozzle orelbow can be rotated between two outlet positions of the water jetdownward or upward, in which no propulsive force is produced, the outletpositions of the water jet of the front and rear motions being at 90°from either vertical position.
 7. Unit according to claim 5,characterized in that the locking plate has a circular sector intendedto block the opening of the outlet nozzle at least partially, when theoutlet nozzle is rotated to an intermediate position at 45° from eitherof the vertical positions of said outlet nozzle.
 8. Unit according toclaim 6, characterized in that an intermediate position of an outletnozzle at 45° from either of the vertical positions of said outletnozzle places the openings existing in each of the tubes opposite oneanother, the backflow jets being directed to pipes in front and in back,one ending in a nozzle situated at the rudder post and the other in apivoting nozzle situated under the third bow.
 9. Unit according to claim8, characterized in that spherical valves are mounted on the pipes infront and in back in order to quickly fill trimming tanks, one situatedin front and the other in back in the space between hulls.
 10. Unitaccording to claim 9, characterized in that spherical valves are mountedon the pipes in front and in back in order to quickly fill tanks formedby the walls of the hulls lined inside the boat by a tight bulkheadgoing from the upper deck to the water line.
 11. Unit according to claim1, characterized in that it further contains additional means ofpropulsion, consisting of a motor pump provided in each hull in back ofthe motors of said unit, also usable as a fire pump, while the boatremaining maneuverable.